Deuterostome clade



  • Phylum Echinoderms (Invertebrates)
  • Phylum Chordata (mostly Vertebrates)
    • Independent evolution of each group


  • Deuterostome = Developmental similarities
    • radial cleavage
    • anus from blastopore


  • HOWEVER: other basal animal phyla share some of these traits
    • Deuterostomes now defined by DNA

Protostome vs Deuterostome






  • Protostome = First Mouth


  • Deuterostome = Second Mouth


  • Two groups differ by embryonic development

Sexual reproduction in animals results in diploid zygote


Phylum Echinoderms



  • Translates to ‘Spiny Skin’
    • sea stars and urchins
    • slow moving and marine
    • adult = radial, larval = bilateral


  • Thin epidermis covered in hard plates
    • often with bumps or spines

Phylum Echinoderms



  • Translates to ‘Spiny Skin’
    • sea stars and urchins
    • slow moving and marine
    • adult = radial, larval = bilateral


  • Thin epidermis covered in hard plates
    • often with bumps or spines


  • Possess a unique water vascular system
    • flexible hydraulic canals = tube feet

Phylum Chordata (mostly vertebrates)



  • All chordates share 4 traits
  • Some only in embryo stages
  1. Notochord
  2. Dorsal, hollow nerve cord
  3. Pharyngeal slits
  4. Muscular, Post-anal tail


  • 2 invertebrates groups that are more related to vertebrates
    • Cephlachordata (lancelets)
    • Urochordates (tunicates)

Lancelets and Tunicates


Vertebrates are chordates with a backbone





  • Possess skeletal and nervous systems
    • simple to complex backbones
    • lots of unique genes (eg. HOX)



  • Derived trait = neural crest
    • special cells near neural tube in embryo
    • give rise to many vertebrate traits
    • e.g.. teeth, skull cartilage, etc

History of backbones: ~525 million years old



  • Evolved while predators where developing
    • Cambrian period
    • Ocean origins (first 150 mya)


  • Vertebrate: series of bones that make up the vertebral column
    • 57,000 species


  • Vertebrates with limbs colonized land 365 mya
  1. Amphibians
  2. Reptiles (w/ birds)
  3. Mammals

Hagfish and Lampreys



  • Only members of vertebrates without jaws
    • sister group of jawless fish


  • Have rudimentary backbones
    • more cartilage than bone


  • Hagfish escape by releasing slime
    • researched to stop bleeding in surgery

Hagfish and Lampreys



  • Only members of vertebrates without jaws
    • sister group of jawless fish


  • Have rudimentary backbones
    • more cartilage than bone


  • Hagfish escape by releasing slime
    • researched to stop bleeding in surgery


  • Many Lamprey are parasitic on fish
    • invaded Great Lakes
    • native to Chesapeake Bay

Vertebrates with jaws


Sharks and rays



  • ‘Cartilage fishes’: skeletons mostly cartilage
    • often with calcium
    • originated 400 mya


  • Streamlined body for swift swimming
    • poor maneuverability
    • near constant motion


  • Birth via eggs or young develop inside mother


  • Modern species diversity shrinking

Ray-finned and Lobe-finned fish








  • Phylogeny: large new vertebrate group with bony endoskeletion
    • fishes = aquatic groups


Add lungs/lung derivatives to phylogeny

Ray-finned and Lobe-finned fishes (lungs on phylogeny)




  • Important derived traits for fishes:
    • operculum:
    • swim bladder:


  • Ray-finned: bony rays that support fins
    • trout, sea horses, eels


  • Lobe-finned: rod-shaped bone surrounded by muscle in fins
    • lungfish, Coelacanths, earliest tetrapods

Evolution had to solve a density problem for bony fishes




  • A fish has a density of about 1.076
    • freshwater has a density of 1.0
    • saltwater has a density of 1.026


  • Bone is nearly twice as dense as cartilage


  • Swimming is energy expensive
    • resting on the bottom may not be practical


  • Evolution of the swim bladder set fish free